Fastest way to compare a string with an array of strings in C#2.0

What kind of comparison do you want? Do you want to know if the given string is in the array?

bool targetStringInArray = array.Contains(targetString);

do you want an array of comparison values (positive, negative, zero)?

var comparisons = array.Select(x => targetString.CompareTo(x));

If you're checking for containment (i.e. the first option) and you're going to do this with multiple strings, it would probably be better to build a HashSet<string> from the array:

var stringSet = new HashSet<string>(array);if (stringSet.Contains(firstString))  ...if (stringSet.Contains(secondString)) ...if (stringSet.Contains(thirdString))  ...if (stringSet.Contains(fourthString)) ...

You mean to see if the string is in the array? I can't remember if arrays support the .Contains() method, so if not, create a List< string >, add your array to the list via AddRange(), then call list.Contains({string to compare}). Will return a boolean value indicating whether or not the string is in the array.

If you are doing this many times with a single array, you should sort the array and binary search it:

Array.Sort(array);int index = Array.BinarySearch(array, input);// if (index < 0) //      does not exists, "items > ~index" are larger and "< ~index" are smaller// otherwise, "items > index" are larger and "< index" are smaller.

Otherwise just check the whole array naively:

bool exists = Array.IndexOf(array, input) >= 0;